I am trying to register a repository that sits behind an https:// URL
and requires authentication. zypper appears to automatically detect such
URLs as services instead of repositories.

What's the zypper command you're using to register the repo?

If it was 'zypper ar', please open a bugreport and attach the zypp.log.

I realize now that the problem is more fundamental. I am trying to
register a repository on a server that uses iChain authentication. Is
this possible with zypper? If yes, how/where is the login information
registered?